Samson did not commit suicide (Judges 16:23-31). What he did, he did as an act of war. He was acting in the capacity of a Judge of God's people whose duty it was to fight the pagans. Just look at the other judges and it is clear what they were charged to do; throw off the yoke of the idolaters. Samson just happened to be in a situation where he would die along with them. Yet, he was doing it as a servant of God, soldier of Israel.
Also, Samson is going to heaven. If not, then why is he exalted along with Abel, Noah, Abraham, Moses, and Joshua in Hebrews 11? Seems pretty clear to me.
Suicide is sinful because it is the unlawful taking of life. God gave us life and it is up to Him (through the laws of nature) to take it away. This includes old age, disease, or accidents. In the case of the mentally ill, I reserve judgment. God will determine if that person was accountable at the time of his/her death.
— Steven F. Deaton
It is troubling that a child of God would consider suicide. To me, this means they have lost hope or nearly lost it. This is one of the tools the devil uses against us. He wants us to think life is terrible, will get no better or will get worse, and end it all. If he can do this, he has taken one more soul and a potentially influential servant of God off the battle field.
God requires us to offer ourselves to Him. Paul said, “I beseech you therefore, brethren, by the mercies of God, that you present your bodies as a living sacrifice, holy, acceptable to God, which is your reasonable service” (Rom. 12:1). The key for us is “living sacrifice.” We cannot be a living sacrifice if we take our own life.
One preacher said it is the most selfish thing a person can do. He’s right. Some think taking their life will solve the problems they have caused for themselves and others. Rather than this, it leaves more serious and long-lasting problems for the family who is left behind.
If you are considering taking your life, tell your spouse or a strong brother or sister in Christ. Get help quickly. Pray to God for strength. Also, consider those who had many difficulties in their lives, but chose to press on in service to God: Job, Peter, Paul. Job lost his property and children, but remained faithful to God. Peter was guilty of denying the Lord he swore to defend, yet he kept it together and went on to be a major impact on the cause of Christ. Paul was guilty of persecuting Christians, even to death. However, his guilt and grief over this did not hold him back from serving Jesus daily. Are we in any worse condition or situation than they?
Keep the faith!